Calvin Klein's underwear ads have always been notoriously risqué: Consider Kate Moss's topless pose in 1992, when she was 17. Or the 1985 ad featuring a half-nude woman sandwiched between two strapping young men on a bed. Or the 2010 image with five partially-clothed models piled on a couch in particularly suggestive poses.

The brand's decidedly NSFW spring ad campaign — wherein models personalize the tagline "I _____ in my calvins" — is no exception. But one image in particular has caused a bit of a social media uproar (and no, it's not Kendall Jenner holding a particularly lurid grapefruit half).

The ad features Klara Kristin, shot from below — wayyyy below. We see her tousled blonde head staring down at us, but mostly we see her legs and the crotch of her blue-and-white dotted panties.  The Danish actress is 23, though some critics insist she appears quite a bit younger in this photo, which may be why the brazen up-skirt angle shocked so many people. (Below, some of Kristin's more family-friendly poses.)

"NOT OK," wrote one woman on Instagram.

"This is depraved," wrote another.

"I guarantee this shot will be downloaded on every Pervert's computer," added another, insisting that Calvin Klein is "making the world a (less) safe place for our daughters, sisters & wives."

Others just shrugged, pointing to Calvin Klein's long history of pushing boundaries and cultivating controversy, an approach that has come to define its brand.

"I get it. The ad has people talking and that is the point," said one Instagrammer. "I love this."

Calvin Klein did not immediately respond to a request for comment. Other fashion insiders have weighed in to defend the ad.

"Calvin Klein has always been a thought-provoking brand," Craig Lawrence, president of One.1K Model Management, told Fox. "Brooke Shields was a child when she was quoted as saying 'nothing comes between me and my Calvins.' Was that child porn? In my opinion, it wasn't then, and it isn't now."

Calvin Klein. the legendary founder of the reliably buzzy company, at the Fashion Institute of Technology in New York last week. (Matthew Eisman/Getty Images for FIT)

But the National Center on Sexual Exploitation disagreed, arguing that the ad glamorized sexual harassment. The group launched a petition demanding that the image be removed from the ad campaign.

"Up-skirting is a growing trend of sexual harassment where pictures are taken up a woman's skirt without her knowledge, or without her consent," said Dawn Hawkins, the organization's executive director, in a prepared statement. "Calvin Klein is sending a message that the experiences of real-life victims don't matter, and that it is okay for men to treat the woman standing next to them on the metro as available pornography whenever they so choose."

Calvin Klein has faced critics, bans and petitions before — as well as accusations of championing "kiddie porn" (in 1995, the FBI and U.S. Department of Justice launched an investigation of a racy ad featuring young, half-dressed models posed in what looked like a suburban basement; the probe found no evidence of wrongdoing). At this point, it's hardly shocking that the designer would produce a shocking image. But not everyone thinks that's an excuse: "It smacks of desperation," wrote one Instagram user below the image of Kristin, adding the hashtag #notallpublicityisgoodpublicity.

As of Thursday, the controversial image had 44,500 likes on Instagram.